Cell Biology Exam 1

Stem cells

unspecialized cells that have self renewal abilities and can differentiate into any cell an organism possess

Totipotent

develop into any cell and present in early development

Pluripotent

develop into any cell within the 3 germ cells but cannot form an organism by itself

Multipotent 

develop into any cell in the body derived from a certain germ layer 

Unipotent

develop into one type of cell or tissue 

Cell Theory (Schleiden, Schwann, Virchow)

All living things are composed of cells

Cells are the basic unit of structure and function for an organism 

Cells only come from pre-existing cells

20th Century Biology

Reductionistic approach—understands by breaking down a complex system into smaller pieces 

DNA sequence

raw DNA sequence with computational tools to identify open reading frames

Gene circuits

regulatory networks of genes and their products that control where and how much a product is made

Modern High-Throughput Technologies Pathway

DNA sequence→ Genes → Gene product → gene circuits 

21st century Biology

integrative approach—looking at the whole system by combing parts together 

Phenomics

the study between phenotypes and genotypes

Mass and Energy GC

metabolism and transport

Information Transfer GC

transcription, translation, and signal transduction

Cell Fate GC

cell motion divisions, adhesion, differentiation

Macro cell components

proteins (~50–60% of dry mass), nucleic acids (~15%), polysaccharides (~10%), lipids (~5–10%)

Micro cell components

organic molecules, inorganic ions (salts)

Crowding

the idea that due to multiple processes the components within a cell have limited space

Eukaryote water percentage (AC)

70%

Integrated functions

the meshing of multiple gene products due to a crowded cell environment

Eukaryote protein percentage (AC)

15%

Eukaryote metabolite percentage (AC)

1-3%

Eukaryote DNA percentage (AC)

1%

Eukaryote volume (AC)

4000 microns ³

Cell diffusion speed

often fast, milliseconds

cell metabolism speed

often slower

Numerical Aperture

a measure if a lens ability to gather light and resolve fine specimen detail

higher NA= better detail 

Light microscope

uses visible light passed through or reflected from a sample ; magnified by lenses for visualization and sharpened by phase contrast

Fluorescent Microscope

high intensity light to excite fluorescent dyes or proteins, only tagged parts of the cells emit visible light

FM excitation

= light absorbed

FM emission

= longer wavelength light released

Atomic Force Microscope

measures surface topography with a probe, the tip
is repelled by or attracted to the surface, the cantilever beam deflects, the magnitude of the deflection is captured by a laser that reflects at an oblique angle from the very end of the cantilever

AFM Contact mode

tip is in continuous physical contact with the sample surface while scanning, measuring forces directly

AFM Tapping mode

intermittent contact, tip oscillates and lightly “taps” the surface at the end of each swing, reducing damage to soft samples and minimizing lateral forces

Confocal Microscope

uses lasers and a pinhole to eliminate out-of-focus light, produces sharp, thin “optical sections” that can be stacked into 3D images

Electron microscope

uses an electron beam of light to a much higher resolution (nm range)

TEM

transmission electron microscope, internal structures

SEM

scanning electron microscope, surface detail

Molecular beacon

recognition based on fluorescent energy transfer, hairpin DNA with fluorophore + quencher → fluorescence only when bound to target

FRET

energy transfer between donor and acceptor fluorophores, when close → measures protein interactions

Cytoplasm

contents of a cell excluding the nucleus

cytosol

the fluid portion of the cytoplasm suspends the organelles 

centriole

a cylinder of 9 triplets of microtubules held together by supporting proteins (9+0 array)  

microtubules

hollow tubes made out of tubulin that provide strength and support, movement of cellular structures

microfilaments 

double helix polymer of actin that possesses directionality and aids in cell movement  

cell membrane

a barrier that encases the cell comprised of proteins, cholesterol and lipids

cilia

long extensions containing microtubule doublets in a 9 + 2 array to move material over the surface

proteasomes 

hollow cylinders that contain proteolytic enzymes and regulatory proteins to break down and recycle damaged proteins

ribosomes

RNA + proteins that function in protein synthesis

Golgi apparatus

flattened cisternae that stores, alters, and packages secretory vesicles

mitochondria

double membrane with inner folds enclosing enzymes (95% of ATP synthesis )

ER

network of membranous channels that synthesis secretory products and carry out transport/ storage

peroxisomes

vesicles with degradative enzymes to neutralize toxic compounds generated in catabolism 

lysosomes

vesicle that contains digestive enzymes that removes damaged organelles and pathogens

integral proteins

proteins that span the entire membrane while corresponding to the differing polar/nonpolar regions 

peripheral proteins

proteins found on the outside of the membrane used for communication and support

anchoring proteins

attach the inside/outside structures to stabilize

receptor proteins

bind and respond to ligands

carrier proteins

transport specific solutes through the membrane that normally couldn’t cross 

channel proteins 

regulate water flow and solutes through the membrane (ions+ polar molecules) w/ the concentration gradient 

glycocalyx

sticky sugar coat, Lubrication and Protection, Anchoring and Locomotion, Specificity in Binding (receptors), Recognition (immune response)

Endocrine signaling

hormones secreted and carried through the circulation system to act on distant body sites

Paracrine signaling

signaling molecules with RNA + DNA fragments in the exosomes that are released by one cell to act on neighboring target cells 

Autocrine signaling

cells respond to molecules/signals that are produced by the cell 

Signaling Pathway

Sensors→ Signaling pathway → Gene Expression (Nucleus) →Protein Expression → functions

Direct signaling

cell-cell or cell-matrix (integrins and cadherins)

Stages of signal transduction

1. Reception

2. Transduction

3. Cell response 

1.Reception

reception of an extracellular signal by cell

2.Transduction

processing of the signal from the outside to the inside of the cell (multi-stepped)

3.Response

cells response initiated with in the cell

Exosome Biogenesis

the inward budding of the membrane to form a vesicle and endosome, following another budding to create a multi-vesicular body that contains exosomes

exosomes

extracellular vesicles that contain mRNA,ncRNA, DNA fragments and proteins that can be degraded and transported

NO

a gas that signals to relax smooth muscle and vasodilation 

CO

a gas the signals the brain at low levels

testosterone

a male sex hormone that regulates development of male reprod. tissues

estradiol

primary female estrogen control menstrual cycle and reprod. tissues

progesterone

prepares and maintains uterus for pregnancy

cortisol

stress hormone increase blood-glucose levels

aldosterone

increases sodium and water absorption in kidneys, raises BP

GCPRs

a large class of receptors that detect molecules outside the cell and activate an internal signal

GPCR steps 

ligand binding → conformational change → G-protein activation (GDP→GTP) → effector enzyme → second messenger

common GCPRs

cAMP, Ca²⁺, IP₃, DAG

cell development

the successive process of systematic gene-directed change through organisms life cycle (observable changes in structure/function)

Determination

cell fate committed (not reversible)

fertilization

the sperm and egg fuse together

cleavage

12-24 hour rapid division with no individual cell growth controlled by cyclins and Cdks

blastulation

mass of cells begin to form a hollow ball

differentiation

the cell begins to differentiate and form cavities

implantation

blastocyst implants into endometrium of uterus

Blastomere

a cell produced by division of zygote

blastocyst

a hollow ball, that is the new pluripotent cell that will become part of the embryo

inner cell mass

group of cells inside the blastocyst source of EBSC

hair, skin, nails, spinal cord, peripheral NS

ectoderm (5)

mesoderm (4)

muscle, bone, connective tissue, circulatory system

endoderm (5)

digestive tract, epithelium, stomach, colon, liver

cytoplasmic determinants

molecules that asymmetrically distributed in the egg cytoplasm, direct gene expression 

ESC stages

zygote → morula → blastocyst → inner cell mass

Induction

to change the fate of a cell due to interaction with an adjacent cell

Somatic Nuclear Cell Transfer

a lab strategy for creating a viable embryo from a body and egg cell (micro-pipetting) (cloning)

Reproductive cloning 

A process that creates a genetically identical organism by implanting a cloned embryo into a uterus to develop into a full organism